Development of simple and low-cost technologies for detecting and identifying gases and volatile organic compounds (VOCs) is important for improving human health, safety, and quality of life. Nanostructured forms of carbon, such as carbon nanotubes and graphene, represent an emerging class of materials in chemical sensing. A useful feature of these materials is that their electrical conductance is extremely sensitive to changes in local chemical environment and can be altered by several mechanisms, such as transfer of charge, annealing, and swelling. Dependence on expensive specialized equipment for the fabrication of devices, the need for solution processing, and requirements for chemical functionalization for achieving specificity, however, have limited the applications and wide applicability of these materials. For example, carbon nanotubes (CNTs) are promising materials for sensing of gases and volatile organic compounds; however, their poor solubility in most solvents has hindered the solution-based process of covalent or non-covalent chemical functionalization of CNTs, and the subsequent integration of these materials into devices.
Additionally, methods for fabricating devices with CNTs are often expensive and time-consuming. For example, covalent and non-covalent functionalization of CNTs to generate selective sensing materials in solution often takes hours and sometimes days. Integration of these materials into devices by drop casting, spin coating, and inkjet printing typically requires prolonged drying times to remove solvent, and often involves several repeated processing cycles to obtain devices with desired electrical properties. Furthermore, known methods for fabricating such devices often require the use of toxic solvents, surfactants, or prolonged sonication for dispersing materials in solution.